While Fendi may have eschewed athleisure in its latest collection, it is one of the few companies to ignore the trend. In fact, athleisure has become such an unstoppable phenomenon that it will be added to the dictionary sometime early this year. According to The New York Times, Merriam-Webster will define “athleisure” as “casual clothing designed to be worn for both exercising and for general use.” It is this very definition that makes athleisure such an adoptable trend. It appeals to a wide variety of consumers because it is applicable for almost every situation: going to the gym, grabbing coffee or brunch with friends, running errands and even working in the office.

More flexible dress codes and increased emphasis on staying in shape have contributed greatly to the wide adoption of athleisure. With the rise of the health- and tech-conscious millennial, “consumers are prioritizing health and well-being, with the Internet aiding in the knowledge share,” notes Katie Smith at EDITED. “We may not be exercising more, but we certainly have an increased understanding of wellness,” she says. This, combined with a relaxed dress code in the office, has allowed athleisure to penetrate a large portion of the apparel market.

Take the rise of sneaker culture, for example. Far beyond a fitness necessity, certain kinds of sneakers have become collectibles—and they often come with hefty price tags. They have even been incorporated into formalwear. And, as fashion continues to move away from strict categorizations of formalwear and streetwear, we will continue to see athleisure take on a larger role in the market.

The rise in athleisure has given apparel sales a significant boost in the last couple of years. In 2014, US consumers spent $323 billion on apparel, footwear and accessories, according to The NPD Group. This was a $2 billion increase from the prior year, and largely thanks to dramatic growth in sales of activewear. Morgan Stanley predicts that, by 2020, activewear will represent $83 billion in sales, “stealing market share from non-athletic apparel.” According to Stylus, “The athleisure phenomenon looks set to continue into 2016 and beyond, and is now on course to become one of the fastest-growing global apparel product categories in the second half of this decade.”

This growth in market size is understandable when you look at the growth in new products and the average prices of athleisurewear. For instance, there are currently three times as many sneakers on the market as there are skinny jeans. Sneakers are also expanding into the luxury market, accounting for 25% of new arrivals in 2015, compared to 15% the year prior. According to The NPD Group, the athletic footwear industry grew by 8% in the US last year, generating $17.2 billion. Unit sales increased by 3% and the average selling price was up 5%, to $61.15. And yoga pants, the bread and butter of athleisure, have experienced even more dramatic growth. New arrivals grew 341% in a three-month period in 2015, compared to the same period in 2014. Meanwhile, according to EDITED, the average price for yoga pants increased by 14% as luxury brands such as Lucas Hugh entered the market.

The athleisure market, with its high growth potential and increasing prices, has even caught the attention of the fashion and beauty industries. Athleisure has taken on a higher-fashion spin as celebrities and designers have collaborated with sportswear and fast-fashion companies on limited-edition offerings. From Kanye West and Stella McCartney partnering with Adidas to Beyoncé and Topshop to Alexander Wang and H&M, collaborations have catapulted athleisure to a must-have, offering consumers a more accessible way to wear their favorite, and often very pricey, designers in their everyday lives.

Birchbox, the beauty subscription startup, launched an athleisure beauty brand called Arrow that is “designed to keep up with your on-the-go, active life—whether that means going straight from Pilates to brunch or just powering through an action-packed, appointment-filled day.” With these market segments, it becomes clear that there is an important style aspect to athleisure. This can be seen in the quick adoption of athleisure into street style. Take Lululemon’s lab collections, for example; the company is looking to create functional collections that speak to the unique style of the city.

Athleisure shows no sign of slowing down, which means that new players are joining the game and that new marketing strategies will be key for capturing market share. Kate Hudson’s, Fabletics activewear line is disrupting the space by offering a lower-price, but still fashionable, option to consumers. Originally an e-commerce retailer, Fabletics has now entered the brick-and-mortar space, and it plans to open up to 100 stores in the next 5 years. Another retailer that started off online and entered the brick-and-mortar space, activewear startup Outdoor Voices, recently raised $7 million as part of its effort to establish itself in the multibillion-dollar activewear market. To get ahead, Outdoor Voices and other startups need to position themselves as offering more than just stylish yoga pants. They need to demonstrate how they can provide their customers with the complete active lifestyle that fuels the athleisure trend. The importance of incorporating this lifestyle component can be seen in the success of Lululemon and Sweaty Betty, which both offer yoga classes and other events to actively engage customers. However, right now, athleisure remains primarily casualwear. In 2013, while sales of yoga apparel increased by 45%, yoga participation increased by only 4.5%, according to SportsOneSource.

Athleisure’s strength comes from a shift in lifestyle preferences and the broad applicability of the trend. If it becomes acceptable to wear the same outfit to the gym, to work and to a dinner party, consumers might end up investing less in clothing as each piece becomes more versatile. Retailers are going to have to adjust, be more sensitive to trends within the athleisure space and embrace innovation in material (think stretch, breathability and water resistance).

We are keen to see where this trend takes us. Stay tuned for next week’s post, where we will look at activewear with built-in sensors.

I am an award-winning global retail analyst and a specialist in retail innovation and technology. I am the CEO and founder of Coresight Research, a think tank and mentorship network that advises clients on disruptive technologies reshaping today’s global retail landscape. I ...